Antioxidant, Antimicrobial and Cytotoxic Activities of Amides and Aristolactams from Piper wallichii (Miq.) Hand.-Mazz. Stems

Abstract Four amides, namely, piperine (1), pellitorine (2), piperiline (5) and N-trans-p-coumaroyltyramine (7), and three aristolactams, i.e., piperolactams D (3), B (4) and A (6), were isolated from the methanol extract of Piper wallichii stems. Piperiline, piperolactams B and D were obtained from this plant for the first time. Compounds 1, 3, 5, 6 and 7 were evaluated for their antioxidant, antimicrobial and cytotoxic activities. Piperine (1) displayed the highest antioxidant activity in scavenging DPPH radicals with an IC50 value of 94.51 ± 11.91 μM. Piperolactams D (3) and A (6) showed antibacterial activity against Gram-positive bacteria (B. subtilis and S. aureus) with MICs of between 500-1000 μM. All test compounds were cytotoxic to breast cancer (MCF-7) cells, while the aristolactams were more toxic to colon cancer (Caco-2) cells than the amides. Compounds 1, 3, 6 and 7 were moderately cytotoxic to the doxorubicin-resistant MCF-7 subline (MCF-7/DOX). All compounds were non-toxic to normal human fibroblast (NIH/3T3) cells. GRAPHICAL ABSTRACT